I did not like the idea that it was the Go server who should set values
such as request.user or set the role, because this is mostly something
that only the database wants for itself, such as when calling logout. I
am also planning to use these setings for row security with the user’s
id, that the Go application has no need for, but with the current
approach i would need to return it from check_cookie so that it can
return it back to the database when acquiring the connection.
I would have used the same function to set the settings and the role,
but security definer functions—obviously in retrospect—can not set the
role, because then could switch to any role of the user that defined the
function, not the roles they are member of. Thus, a new function.
I did not want to do that every time i needed the database connection
within the same request, because it would perform the same operations
each time—it is the same cookie, afterall—, so new connections are
request scoped and passed along in the context.
With that check_cookie function i realized that the schema of functions
is important, otherwise pgTAP could give me the OK when it finds the
function in a different schema than what i intended.
I do not want to give access to authenticator until i know who the user
is, herefore that function can not be in the numerus schema as the
authenticator user can not see it.
At first i thought that i would need to implement sessions, the ones
that keep small files onto the disk, to know which user is talking to
the server, but then i realized that, for now at least, i only need a
very large number, plus the email address, to be used as a lookup, and
that can be stored in the user table, in a separate schema.
Had to change login to avoid raising exceptions when login failed
because i now keep a record of login attemps, and functions are always
run in a single transaction, thus the exception would prevent me to
insert into login_attempt. Even if i use a separate procedure, i could
not keep the records.
I did not want to add a parameter to the logout function because i was
afraid that it could be called from separate users. I do not know
whether it is possible with the current approach, since the settings
variable is also set by the same applications; time will tell.
I honestly do not remember why i thought i needed the find_user
function: it is just a select with a query that i only need in a single
place—when login.
I belive it was a missguided attempt to “write the function safer”, in
hopes that calling a function won’t have the same problems as when
querying a table, but this is fixed with the search_path, that i added.
There is no pgTAP for this, i believe.
According to PostgreSQL’s manual[0]:
“STABLE indicates that the function cannot modify the database, and
that within a single table scan it will consistently return the same
result for the same argument values, but that its result could change
across SQL statements.”
This definition matches both functions. Moreover, find_user_role did
not need to be written in plpgsql, that i assume—but did not test—are
slower than sql functions.
[0]: https://www.postgresql.org/docs/14/sql-createfunction.html
User authentication is based on PostgREST’s[0]: There is a noninherit
role, authenticator, whose function is only to switch to a different
role according to the application’s session. Accordingly, this role has
no permission for anything.
The roles that this authentication can switch to are guest, invoicer, or
admin. Guest is for anonymous users, when they need to login or
register; invoicers are regular users; and admin are application’s
administrators, that can change other user’s status, when they have to
be removed or have they password changed, for example.
The user relation is actually inaccessible to all roles and can only be
used through a security definer function, login, so that passwords are
not accessible from the application.
I hesitated on what to use as the user’s primary key. The email seemed
a good candiate, because it will be used for login. But something rubs
me the wrong way.
It is not that they can change because, despite what people on the
Internet keeps parroting, they do not need to be “immutable”, PostgreSQL
can cascade updates to foreign keys, and people do **not** change email
addresses that ofter.
What i **do** know is that email addresses should be unique in order to
be used for login and password, hovewer i had to decide what “unique”
means here, because the domain part is case insensitive, but the local
part who knows? I made the arbitrary decision of assuming that the
whole address is case sensitive.
I have the feeling that this will bite me harder in the ass than using
it as the primary key.
[0]: https://postgrest.org/en/stable/auth.html
jordi fita mas